Introduction: The prognosis of individual patients with IPF is difficult to predict and the clinical parameters are limited. Fibrocytes are bone marrow derived cells capable of producing extracellular matrix (ECM) components. They are involved in wound repair, tissue regeneration, and angiogenesis and they may be involved in progression of pulmonary fibrosis. The objective of the study was to quantify circulating fibrocytes in patients with stable disease and acute exacerbation (AE) and to explore the role of fibrocytes as a biomarker.

3 IPF patients who survived an AE had a decline in fibrocyte levels after resolution of the exacerbation

Fibrocyte levels did not correlate with any of the explored physiologic parameters of severity (FVC, TLC, DLCO, or 6MWT distance)

Fibrocyte levels did correlate with time to mortality but not independently of the exacerbation events

Expert Opinion:

Fibrocytes continue to be of great interest in the pathobiology of IPF. This paper exemplifies two very important points and raises several others. Despite small control groups, the authors demonstrate a higher level of fibrocytes in the peripheral circulation of IPF patients than in normal controls or those with ARDS. They also demonstrate a higher level of fibrocytes in those with "acute exacerbation" of IPF

The limitation of this paper is that while the fibrocyte level correlated with mortality, the numbers of patients were too small to separate exacerbations from higher fibrocytes as independent predictors of mortality.

Nonetheless, the findings should encourage investigation into the role of fibrocytes in the pathobiology of IPF and, in particular, in the acute exacerbation of IPF, a serious and frequently terminal event.